package azure_batch

import (
	"context"
	"crypto/hmac"
	"crypto/sha256"
	"encoding/base64"
	"fmt"
	"net/http"
	"strings"
	"time"

	regexp "github.com/wasilibs/go-re2"

	"github.com/trufflesecurity/trufflehog/v3/pkg/detectors"
	"github.com/trufflesecurity/trufflehog/v3/pkg/pb/detector_typepb"
)

type Scanner struct {
	client *http.Client
	detectors.DefaultMultiPartCredentialProvider
}

// Ensure the Scanner satisfies the interface at compile time.
var _ detectors.Detector = (*Scanner)(nil)
var _ detectors.CustomFalsePositiveChecker = (*Scanner)(nil)

var (
	defaultClient = detectors.DetectorHttpClientWithNoLocalAddresses
	// Make sure that your group is surrounded in boundary characters such as below to reduce false positives.
	urlPat    = regexp.MustCompile(`https://(.{1,50})\.(.{1,50})\.batch\.azure\.com`)
	secretPat = regexp.MustCompile(`[A-Za-z0-9+/=]{88}`)
)

// Keywords are used for efficiently pre-filtering chunks.
// Use identifiers in the secret preferably, or the provider name.
func (s Scanner) Keywords() []string {
	return []string{".batch.azure.com"}
}

// FromData will find and optionally verify Azurebatch secrets in a given set of bytes.
func (s Scanner) FromData(ctx context.Context, verify bool, data []byte) (results []detectors.Result, err error) {
	dataStr := string(data)

	urlMatches := urlPat.FindAllStringSubmatch(dataStr, -1)
	secretMatches := secretPat.FindAllStringSubmatch(dataStr, -1)

	for _, urlMatch := range urlMatches {

		for _, secretMatch := range secretMatches {

			endpoint := urlMatch[0]
			accountName := urlMatch[1]
			accountKey := secretMatch[0]

			s1 := detectors.Result{
				DetectorType: detector_typepb.DetectorType_AzureBatch,
				Raw:          []byte(endpoint),
				SecretParts: map[string]string{
					"url":         endpoint,
					"account_key": accountKey,
				},
				RawV2:    []byte(endpoint + accountKey),
				Redacted: endpoint,
			}

			if verify {
				client := s.client
				if client == nil {
					client = defaultClient
				}
				isVerified, err := verifyMatch(ctx, client, endpoint, accountName, accountKey)
				s1.Verified = isVerified
				s1.SetVerificationError(err)
			}

			results = append(results, s1)
			if s1.Verified {
				break
			}
		}
	}

	return results, nil
}

func verifyMatch(ctx context.Context, client *http.Client, endpoint, accountName, accountKey string) (bool, error) {
	// Reference: https://learn.microsoft.com/en-us/rest/api/batchservice/application/list
	url := fmt.Sprintf("%s/applications?api-version=2020-09-01.12.0", endpoint)

	date := time.Now().UTC().Format(http.TimeFormat)
	stringToSign := fmt.Sprintf(
		"GET\n\n\n\n\napplication/json\n%s\n\n\n\n\n\n%s\napi-version:%s",
		date,
		strings.ToLower(fmt.Sprintf("/%s/applications", accountName)),
		"2020-09-01.12.0",
	)
	key, _ := base64.StdEncoding.DecodeString(accountKey)
	h := hmac.New(sha256.New, key)
	h.Write([]byte(stringToSign))
	signature := base64.StdEncoding.EncodeToString(h.Sum(nil))

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, http.NoBody)
	if err != nil {
		return false, err
	}

	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", fmt.Sprintf("SharedKey %s:%s", accountName, signature))
	req.Header.Set("Date", date)
	resp, err := client.Do(req)
	if err != nil {
		// If the host is not found, we can assume that the endpoint is invalid
		if strings.Contains(err.Error(), "no such host") {
			return false, nil
		}
		return false, err
	}
	defer func() { _ = resp.Body.Close() }()

	switch resp.StatusCode {
	case http.StatusOK:
		return true, nil
	case http.StatusForbidden:
		// Key is either invalid or the account is disabled.
		return false, nil
	default:
		return false, fmt.Errorf("unexpected status code %d for %s", resp.StatusCode, url)
	}
}

func (s Scanner) IsFalsePositive(_ detectors.Result) (bool, string) {
	return false, ""
}

func (s Scanner) Type() detector_typepb.DetectorType {
	return detector_typepb.DetectorType_AzureBatch
}

func (s Scanner) Description() string {
	return "Azure Batch is a cloud service that provides large-scale parallel and high-performance computing (HPC) applications efficiently in the cloud. Azure Batch account keys can be used to manage and control access to these resources."
}